`(13/23+−15/4)+(10/23−1/4−2/7)`
`=−293/92+(−65/644)`
= `−23/7`
b) `(3/4)^2.4^2−(−12)^2:2−2 3/4`
= `9−1/8−11/4`
= `7/18−11/4`
= `4/98`
c) `(17 1/3−18.0,75):23/3+15,75`
= `(52/3−27/2). 3/23+63/4`
= `23/6.3/23+63/4`
= `1/2+63/4`
= `65/4`
` cho mk 5* +ctlhn`